Oven-thermometer.



C. D. BOLIN & L. E. MORE.

OVEN THERMOMETER.

APPLICATION FILED AuG.27. 191s.

1 1 4 1 ,926 Patented June 8, 1915.

l MUM THE MORRIS PETERS CO.. PHOTULITHD., WASHINGTON. DC.

N ,STATEN PATENT @FFlQlit CI-ARLES D. BOLIN AND LUCIUS E. MORE, OF ST. LOUIS, MISSOURI, ASSIGNORS TO NATIONAL THERMO COMPANY, F ST. LOUIS, MlSSOURI, .A CORPORATION (3F-MIS- SOURI.

OVEN-THERMOMETER.

Specication of Let-ters Patent.

Patented June 8, 1915.

Application filed August 27, 1913. Serial No. 786,850.

To all 'whom it may concern:

Be it known that we, CHARLES D. BoLIN and Lucius E. Moen7 citizens of the United States, and residents of the city of St. Louis and Sta-te of Missouri, have invented a new and useful Improvement in Oven- Thermometers, of which the following is a speciiication.

Our invention relates to thermometers of the type wherein a bimetallic spring forms the heat sensitive element, the distortion of which measures the degree of heat to which the device is exposed, indicating mechanism actuated by the spring through multiplying levers being provided to show the amount of distortion and temperature corresponding thereto.

The object of this invention is an improved thermometer of the bimetallic spring type inclosed in a case which is adapted to be secured within an oven door with its back wall exposed to the full heat of the oven and its front wall comprising a dial which is exposed to view.

In oven thermometers of the above type as heretofore made, the heat sensitive element has been curved in the attempt to secure sufficient sensitiveness and quick responsiveness to temperature changes. Such instruments are delicate, diiiicult to adjust, and frequently not uniform in their action, because bending the spring elements causes them to have internal strains which interfere with their responsiveness to heat changes. Moreover, instruments as heretofore made, when fully incased to protect the actuating parts from dirt and grease, are not quickly responsive to temperature changes.

Our invention overcomes the above objections to oven thermometers as heretofore made; and its indications more nearly correspond with the true temperatures as indicated by a mercury thermometer than do the indications of other oven thermometers of the same type, with which we are familiar.

Further objects and advantages of our invention appear in connection with the following description of the embodiment thereof illustrated in the accompanying drawing; and what the invention consists in is pointed out with particularity in the appended claims. Y

1n the drawing, in which like parts are designated by the same reference characters wherever used in the several views,-Figure 1 'is a front view of an oven thermometer made in accordance with our invention; F ig. 2 is a front view of the same with therfront glass, dial and index pointer removed to show the parts within the case; Fig. 3 is a vertical crosssection of the same on the line 3--3 in Fig. l; and Figs. 4, 5, 6 and 7 are perspective views of the bimetallic heat sensitive spring, index-pointer pivot supporting bracket, index-pointer pivot, and indexpointer pivot bearing, respectively.

kReferring to the drawings, our improved device comprises a cylindrical casing 11, having a back wall 12v which forms a support for the heat sensitive spring 13 and indicating mechanism. The back wall 12 has two diametrically opposed ears or lugs 14C provided with slots 15 through which the bolts or screws which secure the device to the door of an oven may be passed. The cylindrical casing 11 projects through the oven door, and a face or dial 16 covers its open front side. Over the dial is a glass 17, held by an outer casing ring 18 which surrounds the casing 1.1A and which has an inturned lip or flange 19 inclosing the glass. A separator ring 20 within the casing ring 18 between the glass and the dial holds the glass spaced away from the dial and in Contact with the flange 19.

The heat sensitive spring 13 is fiat, and is composed of two coextensive leaves 21, 22, secured together latwise, these leaves being made of metals having different coefficients of expansion. such as German silver and steel. The eect of changes in temperature is to bend or bow the spring flatwise. The spring 13 is provided with an integral projection 23 from one side near its end, and this projecting portion is securely riveted through the back wallr of the casing at a point near the lower side thereof. .To the opposite end of the spring 13 is riveted a small block 24 having a pin 25 projecting from its side opposite to the projection 23. Y

The dial 16 is marked with a scale 26 reading from about 100 to about 500 degrees Fahrenheit, and an index-pointer 27, mounted on the outer end of a pivot 28, is arranged to swing over said scale. The pivot is j ouinaled at its inner end in a pivot bearing 29 which is riveted to the back wall 12 of the casing. A bracket 30, riveted to the back wall 12, "forms a support for the pivot near its outer end. A slotted arm '3l is carried by and rigidly .attachedy to the pivot, and thepin 25 carried by the block on the end of the sensitivespring engages the slot 32 in the arm and moves the latter when the spring is bowed by a change in temperature. The bracket 30 carries a lug 33 against which the arm 3l strikes near the end Vof itsswing in the direction of the descending scale of degrees.Y This lug can be bent Yand thereby adjusted to stop thepointer at any desired minimum point on thescale, as at room temperature, for example. v v

lt is evident that a devicemadeas above described Vhas comparatively few parts, which parts are simple in construction and easy to assemble. The heat sensitive spring n. is straight at ordinary room temperature,

and consequentlyy requires no bending or other adjustment, the stop L33 being ad.

justable to suit small variations in the setting ofthe spring. Moreover, as the end Vof therspringextends through the back wall of the casing, it is exposed directly to the heat of the oven, which greatly increases the sensitiveness of the devicev and thequickness with whichit responds to changes in the temperature of the oven. Furthermore, theY casing being completelyclosed on the back oroven side, no dirt, grease or smoke from the Oven can get into vit to gum up or corrode the moving parts, and therefore the device will not become sluggish or inaccurate in the course kof a comparatively short. time, as might be the case if it were not so protected.

Having described one embodiment of our invention in detail, We do not restrict Yoursensitive spring, said spring having one endk projecting through said casing whereby the heat of said oven is conducted directly through both metallic elements of ysaid spring. Y

3. In an oven thermometer, a casing inclosing a bi-metallic heat sensitive spring, said spring having one end secured to and projecting through said casing whereby the heat of said ovenY is conducted directly to and through both metallicl elements of said spring.

4. A bi-metallic spring for an oven ther-k mometer, said spring having two elements each of which has as an integral part there- Y of a lateral projection from one edge mating with the llke projection ofthe other and adapted to be secured to a supportingV casing by passing through an opening in theI wall thereof.

Signed at St. Louis, Missouri, this 25th day of August, 1913. f

-` CHAS. D. BOLIN.

LUCIUS E. MORE.

Witnesses: f

A. M. HoLcoMBE, ANDREW P. KESSLING.

Copies ofthis patent may be obtained for ve cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

